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1、沈陽建筑大學(xué)畢業(yè)設(shè)計(jì)（論文） 附錄一：中文翻譯 關(guān)鍵詞：橋梁；河堤；土工布；膜與土工格柵 英國鎖城大橋 鎖城大橋是橫跨住宅發(fā)展區(qū)的鐵路橋梁。由于工程施工受到周圍建筑與地形的限制，該工程采取加固橋臺(tái)、橋墩與橋面的剛構(gòu)結(jié)構(gòu)，以及預(yù)制欄桿等方法提高了大橋的使用安全程度，并降低了大橋建造與維護(hù)的費(fèi)用。因此，城堡大橋科學(xué)的設(shè)計(jì)方案使工程成本降到最低。 一、 引言 本文描述的是在受限制地區(qū)用最小的費(fèi)用修建一座鐵路橋梁

2、使之成為開放的住宅發(fā)展區(qū)。鎖城地區(qū)是位于住宅發(fā)展十分緊張的韋斯頓超 圖1 鎖城大橋位置遠(yuǎn)景 馬雷的東部。監(jiān)督橋梁建設(shè)的客戶是城堡建設(shè)有限公司，它由二大房建者組成。該區(qū)的規(guī)劃局是北盛捷區(qū)議會(huì)（NSDC）。該發(fā)展地區(qū)被分為布里斯托爾和埃克塞特。規(guī)劃條件規(guī)定，直到建成這條橫跨的鐵路大橋?yàn)橹?，該地區(qū)南部區(qū)域不可能適應(yīng)居住?？梢婃i城大橋的建成對該地區(qū)發(fā)展的重要性。 發(fā)展地區(qū)位于薩默塞特的邊緣，這個(gè)地區(qū)地形十分的惡劣，該范圍位于韋斯頓以北和A321飛機(jī)雙程雙線分隔線的南面?，F(xiàn)在只有一條鄉(xiāng)下公路，是南部區(qū)域的唯一通道。該地區(qū)是交通預(yù)期不適合住宅增加的區(qū)域。 由于盛捷地區(qū)水平高程的限制，新的鐵路線在

3、橋臺(tái)兩邊必須設(shè)有高程差。 并且該地區(qū)地形限制，允許正常橫跨的區(qū)域較小，這導(dǎo)致在結(jié)構(gòu)的布局上的一定數(shù)量的妥協(xié)。為了整個(gè)城堡地區(qū)的發(fā)展， 全圖2 鎖城大橋地圖上位置 橋限速20公里/時(shí)，并考慮區(qū)域范圍內(nèi)的速度制約。這樣在得到客戶和NSDC的同意后，橋梁采取了最小半徑的方法，這使得橋梁采用了比正常梯度更加陡峭地方法實(shí)現(xiàn)高程的跨越。 客戶的工程師、工程顧問、一般設(shè)計(jì)原則和初步認(rèn)同原則下(AIP)與NSDC發(fā)出投標(biāo)文件。 該合同在2000年7月1授予安迪。投標(biāo)價(jià)值1.31億美元，合同期定為34周，到2001年4月完成。

4、 圖3 橋整體橫斷面 圖4 橋體長度 圖5 橋上部結(jié)構(gòu)橫斷面 二、地基 在招標(biāo)階段佩爾研究了一些優(yōu)化設(shè)計(jì)和招標(biāo)后的裁決計(jì)劃進(jìn)行了充分的經(jīng)濟(jì)分析后交付承包商，院長及安迪 。原來設(shè)計(jì)要求H型 圖6 橋面鋪裝 鋼樁柱下的橋臺(tái)地區(qū)與相鄰鐵路線之間必須是垂直運(yùn)動(dòng)。經(jīng)審查后的地面條件和根據(jù)以往的經(jīng)驗(yàn)判斷，現(xiàn)澆位移樁，使用其他類似地方

5、的河堤下，可驅(qū)動(dòng)更接近軌道而不會(huì)有任何問題。并在受影響區(qū)域進(jìn)行了監(jiān)測，打樁作業(yè)和水平高程的變化小于要求的6毫米。 在地面下覆蓋厚達(dá)19米的軟沖積土。這下面是2米層堅(jiān)定/硬粘土泥巖或砂巖基石。兩種類型的驅(qū)動(dòng)現(xiàn)澆樁設(shè)計(jì)了340和380毫 米的大口徑水管，以應(yīng)付不同載入條件所造成的橋梁和堤壩的不同荷載。 這些有利于樁體的載入。最多可達(dá)一天8個(gè)樁的記錄?？傞L度 驅(qū)動(dòng)介于22和24米之間。試驗(yàn)證實(shí)了完整的設(shè)計(jì)和表示最多解決在工作負(fù)荷為六毫米 一個(gè)具體的樁帽負(fù)載從橋墩傳遞到樁。 取代H型樁柱與 驅(qū)動(dòng)現(xiàn)澆樁， 但略有減少水，它能使樁帽的荷載延長傳遞到承臺(tái)，從而節(jié)約施工時(shí)間 以及成本。 三、荷載傳遞

6、，路基 樁被用來抑制端口的負(fù)載轉(zhuǎn)移，這是因?yàn)樾藿〞r(shí)采用了石頭和網(wǎng)膜。 在招標(biāo)圖紙上顯示了基礎(chǔ)頂部擴(kuò)大樁，再運(yùn)用早先經(jīng)驗(yàn)， 佩爾指出這個(gè)設(shè)計(jì)方法可能被運(yùn)用減少墊層的深度，并且把這種方法使用在城堡大橋上。 通過熔鑄一個(gè)擴(kuò)大的部分1.1m在每樁上面，距離到樁下減少了1 m直徑，并且薄膜的間距在墊層的增加因而被減少了。 假設(shè)成拱形的作用在承臺(tái)依靠角度458從堆到墊層的上面，可能相應(yīng)地減少石頭的深度。通過合理的設(shè)計(jì)，墊層的整體深度從1500毫米減少了到900毫米。 這樣減少了挖掘深度并保留了原始的底層。. 墊層路堤上升到最大高度6.3 m的車道高程。為了減少蔓延的路堤，招標(biāo)設(shè)計(jì)最初面臨混凝土預(yù)制板垂

7、直側(cè)壁。這是后來修正的在投標(biāo)階段用紅磚砌筑的垂直墻壁，迫使改變設(shè)計(jì)中的鋼筋路堤。路基被分包兩個(gè)部分以坦薩為基礎(chǔ)和規(guī)范發(fā)展的佩爾弗里斯赫曼恩路段。其系統(tǒng)組成的單軸土工格柵在不同規(guī)定垂直間隔的壓實(shí)顆粒物質(zhì)。顆粒狀材料，符合高速公路規(guī)范做路堤材料的相關(guān)規(guī)定。該網(wǎng)格，掛靠在干燥的混凝土砌塊上形成近垂直的路堤。被垂直排水層分開。在兩者之間安裝了隔水帶，并且在前面修建了磚砌飾面。 圖-4展示基礎(chǔ)的橫斷面。 圖7 防撞墻 路堤的設(shè)計(jì)是依靠緊密的產(chǎn)品的密度結(jié)構(gòu)。這并不會(huì)減少橋梁結(jié)構(gòu)的120年的設(shè)計(jì)使用壽命。此方法的約束結(jié)構(gòu)是眾所周知的, 并且在結(jié)算梁末端的負(fù)彎矩時(shí)作為一個(gè)統(tǒng)一體來解決。并且利用墩臺(tái)的內(nèi)

8、力來約束其相對移動(dòng)。在招標(biāo)圖紙上還限制了必須要保持同樣的深度。現(xiàn)在 從Y3到Y(jié)4進(jìn)行簡化設(shè)計(jì)，這樣就會(huì)有更高的橋基、更大的樁和橋梁荷載，造成進(jìn)口的材料損失。院長及安迪在這一共同目標(biāo)下進(jìn)行了這項(xiàng)工作。凈厚40毫米的瀝青混凝土不僅滿足材料等級的要求，也適合使用在負(fù)荷傳遞的墊層上。此外，一直在現(xiàn)場進(jìn)行永久材料的測試，而在興建河堤時(shí)，該材料很容易壓實(shí)，按要求使用1.5噸的振動(dòng)壓路機(jī)碾壓，而且，就其性質(zhì)而言，非常適合埋設(shè)在潮濕的條件。所有的測試結(jié)果顯示， 最低的壓實(shí)度在94 ％以上，壓實(shí)度遠(yuǎn)遠(yuǎn)超過承包商期望。 四、橋梁和橋墩 橋面包括預(yù)制預(yù)應(yīng)力混凝土梁和一塊跨度20m的現(xiàn)澆鋼筋混凝土平板。圖4和5顯

9、示橋梁的長度和橫斷面。 在加強(qiáng)的橋臺(tái)建立支撐梁。在支撐梁區(qū)域凸顯了橋臺(tái)狹窄的特點(diǎn)，并且這些太狹窄的橋臺(tái) 圖8 擋土墻 不能避免的退出工作結(jié)構(gòu)，并對混凝土砌塊側(cè)壁的河堤產(chǎn)生壓力。為了克服這個(gè)困難，把河堤的擋土墻在橋臺(tái)附近擴(kuò)大，并使之成為完全擋土墻 (圖8)。 因?yàn)檫@變動(dòng)太大以至于不能掩藏，在磚墻的上面放置的磚砌和預(yù)制混凝土做了加寬的區(qū)域，并在橋臺(tái)附近形成了壩肩。最后的布局給橋梁帶來了增值效應(yīng)并豐富了橋梁和其施工方法。 一旦澆注了混凝土，整個(gè)橋面將形成一個(gè)整體。 這方法消除了梁與支撐之間的轉(zhuǎn)動(dòng)，因此，使橋面形成了一個(gè)統(tǒng)一的更加陡峭坡度。為了保持橋面產(chǎn)

10、生壓力保持一樣，使橋面出現(xiàn)橫向的排水，這是招標(biāo)圖紙不允許的。 這就提出了一個(gè)南部路基高于預(yù)期150毫米。 設(shè)計(jì)要求在梁和橋面板之間容納一些復(fù)雜的服務(wù)設(shè)備。這些設(shè)備是一條250毫米直徑總水管(通過一條350毫米直徑輸送管)， HV電纜和一條四種方式的BT輸送管。在招標(biāo)圖紙上看這些服務(wù)設(shè)備是在橋梁之間缺失的部分通過，而不是在它的下面通過。這些可利用的部分損失能夠使橋梁的自重更小、結(jié)構(gòu)減輕，而且橋梁的截面尺寸更大，這些臨時(shí)的設(shè)施在孔中通過。因此，要求作出詳細(xì)的安裝說明，這又是一個(gè)非常棘手的工作。 橋梁的布局方案是一個(gè)整體的固定結(jié)構(gòu)。并且，重新設(shè)計(jì)成了垂直路線，以適應(yīng)橋面的變化。這就導(dǎo)致了南部橋臺(tái)

11、的升高，從而，橋面的坡度增加。因此，對上面的橋梁產(chǎn)生了連鎖反應(yīng)。為提供合理的橋面跨越坡度，在橋南部的樁相應(yīng)的增長，在增長最多的地方增加深度超過300毫米。這要求在預(yù)應(yīng)力混凝土中增加更大預(yù)應(yīng)力。 在早期階段的合同中，院長及安迪把梁的施工作為一個(gè)關(guān)鍵階段， 尤其施工是在1月份進(jìn)行。承包商要求在梁之間快速安裝永久模板，并且，要求在邊梁設(shè)計(jì)時(shí)插入臨時(shí)扶手欄桿。 澆注了橫跨橋梁護(hù)墻后，能夠掩蓋P6欄桿末端。在安裝邊緣梁之前應(yīng)先安裝臨時(shí)扶手欄桿。在安裝所有的混凝土梁之前，承包商先安置永久模板。這種安裝方法安裝11根梁和所有的永久建筑僅僅需要5小時(shí)，大大的節(jié)省了施工周期。 五、護(hù)墻 標(biāo)準(zhǔn)型的P2護(hù)墻

12、的目的是保護(hù)的邊緣河堤。因此，對該小組提出了相當(dāng)大的挑戰(zhàn)。必須在原先的位置澆注鋼筋混凝土，承包商對這種解決方案提出了健康與安全問題，因?yàn)樵诘孛嫔蠞沧?m的邊緣梁是十分危險(xiǎn)的，必須要用到更多的腳手架和永久模板，并且，施工將延長幾個(gè)星期，工期將更加緊張。 為此，承包商建議使用預(yù)制混凝土欄桿來替代在原處澆注混凝土。然而，由于橋梁采用的是最小半徑，所以每個(gè)混凝土梁的長度受到限制，以避免出現(xiàn)外觀問題。并且計(jì)算表明混凝土欄桿會(huì)受到使用限制。 另外一種折衷的解決辦法包括一個(gè)預(yù)制件和邊緣現(xiàn)澆的行人/自行車道建設(shè)，最終克服了這些問題。為了實(shí)現(xiàn)理想的效果，邊梁的預(yù)制需要的足夠的大小和形狀的磚塊，以確保

13、邊緣的路堤穩(wěn)定。此外，雙方每個(gè)單位將需要略錐形，以適應(yīng)半徑的彎道，并且護(hù)墻后螺栓支持搖籃要預(yù)先安裝在正確的間距上。由于設(shè)計(jì)師和承包商通力合作，盤區(qū)類型的數(shù)量從30減少到17，排列在長度從最多3.65 m減少到最小限度1.98 m，并保留欄桿位置恒定間距沿堤防的主要長度（如圖9）。 預(yù)制的構(gòu)件通過現(xiàn)場澆注在一起，形成了一個(gè)整體。同時(shí)連欄桿和擴(kuò)大的路堤也澆注在一起。把橋面板澆注在一起，使之形成梁。并且橋面板做了腳趾形設(shè)計(jì)，利用其摩擦力來抵抗欄桿的偶然荷載，用連續(xù)的橋面板和懸臂式結(jié)構(gòu)抵抗外部的對 橋面的扭轉(zhuǎn)和傾覆力。 P2支持部分被做成水平并且與橋梁完美的組合在一起。而末端被混凝土掩蓋保證了外觀

14、的整潔。 六、運(yùn)作 在整個(gè)計(jì)劃中最值得欣慰的是能夠很好的維護(hù)各個(gè)方面的關(guān)系。大家在工程合同約定下一起工作，在出現(xiàn)矛盾之前，舉行定期會(huì)議時(shí)告知承包商、設(shè)計(jì)師、客戶的工程師和客戶的建筑師工程之間相互通告事情的最新事態(tài)發(fā)展和處理的意見。并且在感興趣的方面打開信息交換的通道適時(shí)的通信，例如處理好鐵路軌道等，并按要求保證資金適時(shí)到位。在遇到工程最后期限緊張時(shí)或發(fā)現(xiàn)設(shè)計(jì)圖紙有小遺漏時(shí)要以專業(yè)的方式進(jìn)行溝通。這事成為承包商在整個(gè)合同期間維護(hù)信用的關(guān)鍵。 七、摘要 鎖城大橋是集現(xiàn)代和創(chuàng)新于一體的設(shè)計(jì)（圖9）。加上其美麗的外觀，不僅美化了當(dāng)?shù)丨h(huán)境。還增加了外界聯(lián)系。更有利于新住宅的發(fā)展。并且在橋的南部還

15、建立了一個(gè)公園，這將提高大橋的地位和整體的外觀。在今后幾年里，鎖城大橋?qū)⑹撬袇⑴c建造者的自豪。 圖9 鎖城大橋 參考文獻(xiàn) 公路工程規(guī)范 速公路局辦公室 1993年 建筑與土木工程規(guī)范 建造與設(shè)計(jì)辦公室 1998年 附錄二：翻譯原文 Castle Bridge, Weston-Super-Mare, UK Castle Bridge is a minimal-cost solution to the dilemmaof a restricte

16、d crossing of a main railway line within a residential development area. The works employs reinforced earth embankments, integrated bridge deck andabutment construction and precast parapet solutions toovercome and minimise the safety, maintenance and costissues associated with the scheme. 1. INTROD

17、UCTION This paper describes a minimal-cost solution to a road bridgeover a railway, on a restricted site, to open up land for residential development. Locking Castle is an area under heavy residential development on the eastern side of Weston-Super Mare. Overseeing the development and client for th

18、e bridge isLocking Castle Limited, a company owned in consortium by two major house builders. The planning authority is North Somerset District Council (NSDC). The development area is splitin half by the Bristol to Exeter main railway line. Planning conditions for the area stipulated that the southe

19、rn area couldnot be inhabited until a crossing of this railway line had beenbuilt. Fig. 1 shows the Locking Castle development and theimportance of the bridge to the area. The development area is situated on the edge of the SomersetLevels, an area noted for its poor ground conditions, and is bounde

20、d by a railway line to Weston to the north and the A321dual carriageway to the south. Moor Lane, an existing countryroad, was the only access to the southern area and was notsuitable for the traf?c expected by the increased housing stock. Owing to the nature of the Somerset Levels, the new road ove

21、rthe railway lines would have to be raised on embankments onboth sides of the track. An area of land had been reserved for the crossing but this area was small in comparison to a normalcrossing, which led to a number of compromises in the layoutof the structure. A blanket 20 mph speed limit, coupled

22、 with area-wide speed restriction measures, coverthewholeLockingCastledevelopment. This enabled the roads to be laid to a tightradius on the approaches to the bridge and also allowed theclient to agree, with NSDC, that steeper than normal gradientscould be used to attain the elevation of the crossin

23、g. The client’s engineer, Arup, agreed general design principlesand the preliminary Approval in Principle (AIP) with NSDCprior to the issue of tender documents. The contract was awarded to Dean & Dyball in July 2000 for atender value of 131 million and the contract period was set at34 weeks for a

24、completion in April 2001. A simpli?edprogramme is shown in Fig. 2. 2. GROUNDWORKS During the tender stage Pell Frischmann looked at a number ofre?nements to the tender design and following the award of thescheme undertook a full value engineering exercise in conjunction with the contractor, Dean &

25、 Dyball. The originaldesign called for steel H-piles under the bridge abutment areasadjacent to the railway line where limited vertical movement ofthe track was essential. Following a review of the groundconditions and based on previous experience, the team successfully argued that cast-in-situ disp

26、lacement piles, usedelsewhere under the embankments, could be driven closer tothe tracks without any problem. The tracks were monitoredduring piling operations and level changes of less than 6 mmwere recorded along the affected section. The ground conditions at the site consist of made groundoverly

27、ing up to 19 m of soft alluvial clay. Below this either a2 m layer of ?rm/stiff clay on mudstone or sandstone bedrockexists. Two types of driven cast-in-situ piles were designed byKeller, 340 and 380 mm in diameter, to cope with the differentloading conditions caused by the bridge and the embankment

28、.These were driven to refusal from the existing ground level. Thepoor ground contributed to rapid pile installation and rates of up to eight piles a day were recorded. The total driven lengthranged between 22 and 24 m. Pile design information is shownin Table 1. Tests con?rmed the integrity of the d

29、esign andindicated a maximum settlement at working load of 6 mm. A concrete pile cap was originally shown above the H-piles todistribute the loads from thebridge abutments to the piles.By replacing the H-piles withthe driven cast-in-situ piles,but at slightly reduced spa-cing, it was possible to el

30、iminate the pile caps and extendsaving on construction time as well as cost. 3. LOAD TRANSFERMATTRESS AND EMBANKMENTS The piles were used to support a load transfer mattress,which was constructed fromlayers of stone and geomembrane grids. Enlarged head piles had been shown on the tender drawing bu

31、t, again drawing on previous experience, Pell Frischmann demonstrated that this design method could be utilised to reduce the depth of the mattress and it was suggested that this approach be employed at Locking Castle. By casting an enlarged head of 11 m diameter at the top of each pile, the distan

32、ce to the next pile was reduced and thus the span of the geomembranes in the mattress layers was decreased. Given that the arching effect in the mattress relies on an angle of 458 from the pile to the top of the mattress, the depth of stone could be reduced accordingly. The overall depth of the mat

33、tress was reduced from 1500 mm to 900 mm by rationalising the design in this way. This also led to savings in reduced excavation to the original ground level (Fig. 3).Above the mattress the embankment rises to a maximum height of 63 m to carriageway level. To reduce the spread of the embankment, th

34、e tender design originally indicated faced precast concrete panels to vertical sidewalls. This was amended later in the tender stage to vertical walls of class A red brickwork, forcing a change in the design of the reinforced embankment. The design of the embankment was subcontracted to Tensar, base

35、d on a speci?cation developed by Pell Frischmann. Their system comprised uniaxial geogrids laid at varying vertical spacing on compacted granular material. Class 6I/J granular material, in accordance with the Speci?cation for Highway Works1was speci?ed and this made up the bulk of the embankment. Th

36、e grids were then anchored to dry-laid interlocking concrete blocks forming the near-vertical face of the embankment. A vertical drainage layer separated the 6I/J material from the concrete blocks. Ties were installed between the joints in the concrete blocks and the class A brickwork facing was con

37、structed in front. Fig. 4shows the embankment crosssection. The design of the embank-ment relies on the density of the compacted product being structure. This does not reduce the design life of the structure which was set at the standard 120 years. Dif?cul- ties with this method of construction are

38、 well known and include accounting for differential settlement, increased hogging moments at the ends of the beams and congestion of steel in the small areas between the beams. Suf?cient structural strength is inbuilt to counteract the stresses of one abutment moving relative to the other. The desig

39、n was also restricted by the need to keep the same depth of beam that had been identi?ed on the tender drawings. Increas- ing the beams from a Y3 to a Y4 would have simpli?ed the design but would have the penalty of higher embankments, larger pile and bridge loads, more imported material at a consis

40、tent value. To facilitate this, Dean & Dyball sourced 40 mm scalpings from Tarmac aggregates which not only consistently met the 6I/J grading but were also suitable for use in the load transfer mattress. In addition, a permanent materials testing presence was kept on site while the embankments were

41、being constructed. The material was very easy to compact, requiring no more than a 15 t vibrating steel roller, and, due to its nature, was very suitable for laying in the generally wetconditions that prevailed at the time. All tests showed tha tminimum compaction of 94% was being achieved and the r

42、ate of rise of the embankment exceeded the contractors’expectations. 4. BRIDGE AND ABUTMENTS The bridge deck consisted of prestressed Y3 precast concrete beams and an in situ reinforced concrete slab spanning 20 mover the railway lines. Figs 5 and 6 show the long- and crosssection of the bridge. T

43、he beams were supported on bankseats founded on the reinforced embankments. The narrow nature of the embankments was accentuated at the bankseat area sand it was soon obvious that these were too narrow to avoidresting the structure on the concrete block sidewalls of theembankments. To overcome this,

44、 the embankments werewidened locally in the vicinity of the abutments to enable thebankseat to sit wholly on the embankment (Fig. 7). As this change was too large to hide, a feature was made of the widened area by the use of strong right angles in the brickwork and pre-cast concrete (PCC) ?agstones

45、laid around the top of the brick wall adjacent to the abutments. The ?nal layout gave added effect and accentuated the bridge and its approaches. Once placed, the PCC beams were cast into each bankseat by the addition of an integral endwall. This eliminated the need for bearings and movement joints

46、, thus creating an integral and steeper gradients on the approach roads. Pressure to keep the deck construction as shallow as possible came also from the discovery that the original tender drawings had not allowed for a deck crossfall to shed water. This raised the southernembankment 150 mm higher t

47、han anticipated. The design was further complicated by the requirement to accommodate services under the bridge deck, between the beams, and through the integral end wall. These services were a 250 mm diameter water main (through a 350 mm diameter duct), an HV electric cable and a four-way BT duct.

48、 The loss of section was overcome by agreement to run the electric cable over the top of the deck, rather than below it, as it was not physically possible to bring it through the identi?ed location on the tender drawings. The loss of available wall section led to the requirement for smaller numbers

49、 of, but larger diameter, bars ?tted around the holes through the endwalls. This is turn made the detailing and ?tting of these bars one of the trickiest elements of the job. Although generally ?xed by the layout of the overall scheme, the vertical road alignment was redesigned to accommodate the

50、change in alignment of the bridge deck. This led to an increased gradient on the southern embankment but also had a knock-on effect on the loading of the bridge. To provide a reasonable rollover across the deck from the steep gradients on either side, the depth of surfacing increased to over 300 mm

51、at its deepest point. This greater loading increased the amount of prestressing in the PCC beams. At an early stage in the contract, Dean & Dyball had focused onthe placing of beams as a critical phase of the scheme,especially as the work was to be undertaken in January. Toaccelerate the placing of

52、 permanent formwork between the beams, the contractor requested that the edge beams bedesigned to include inserts to support the temporary handrails. These were cast in at a depth such that they would be hidden in the ?nal scheme by tails on the high containment precast P6parapet across the bridge.

53、 The temporary handrails were ?tted to the edge beams prior to placement (Fig. 8). This enabled the contractor to start placing permanent formwork before all the PCC beams had been laid. This approach reduced the time of track possession, with the eleven beams and permanent formwork all installed wi

54、thin ?ve hours. 5. APPROACH EMBANKMENT PARAPETS Standard parapets of type P2 were designed to protect the edges of the approach embankments and the support for these presented the team with a considerable challenge. Originally shown as in situ reinforced concrete, it soon became clear that this so

55、lution would provide the contractor with a signi?cant health and safety problem. Casting edge beams 6 m above the ground was potentially dangerous, required a lot of scaffolding mand permanent formwork, and would add weeks to the tight construction programme. To overcome this, the contractor propos

56、ed using precast concrete parapet supports in lieu of in situ. However, due to the tight centreline radii on the bridge approaches (50 m radius), the length of each PCC section would need to be limited to avoid a ‘threepenny piece’ appearance. This created its ownproblems when design calculations sh

57、owed that accidental loadings on the parapet would not be restrained by the use of small discrete PCC units. A compromise solution consisting of a precast edge piece and an in situ section under the footway/cycleway construction was eventually developed to overcome the problems. To achieve the desi

58、red effect, the precast edge beam would need to be of suf?cient size and shape to rest on the brick/block edging of the embankment without being unstable. In addition, the sides of each unit would need to be slightly tapered to accommodate the radii of the bends, and the parapet support post bolt cr

59、adle would need to be pre-installed at the correct spacing. Team work between the designer and contractor led to a reduction in the number of panel types from 30 to 17, ranging in length from a maximum of 365 m to a minimum of 198 m, while keeping the parapet posts at a constant spacing along the ma

60、in length of the embankments (Fig. 9). The precast units were tied together by means of an in situ element. This comprised a slab extending the entire length of the embankments from the bankseats to the end of the parapet units. The slab was cast continuously, without joints, so that it acted as a

61、beam. The slab was designed with a toe, which, together with friction, counteracts the lateral forces from accidental loading of the parapet posts while the overturning forces of any impact are countered by the weight and cantilever effect of the continuous slab. The P2 support sections were placed

62、and levelled to give apleasing sweep and elevation to the bridge while a tail on the PCC unit was included to hide the top of the brickwork wall, ensuring a neat appearance was achieved. 6. TEAM WORKIN One of the most pleasing aspects of the scheme was the goodworking relationship that was maintai

63、ned between all parties. Although working under the General Conditions of Contract for Building and Civil Engineering GC/works/1,2the contractor was keen to espouse the ethics of partnering. Regular meetingsbetween the contractor, designer, client’s engineer and client’s architect took place to keep

64、 all parties informed of the latest developments and to deal with concerns before they became a distraction. Communications, channelled through the contractor, between interested third parties, such as Railtrack and NSDC, were also well managed, which ensured that possessions were granted as request

65、ed and adoption requirements were dealt with swiftly. This approach was key to meeting the tight construction deadline and in dealing with the minor omissions found in the tender design in a professional manner. It is a credit to the contractor that this was maintained throughout the period of the c

66、ontract. 7. SUMMARY Locking Castle Bridge is based on a modern and innovative design which, along with its appearance (Fig. 10), bene?ts the local environment and provides a focal point for the new residential development. The creation of a park adjacent to the southern embankment will enhance the status and appearance of the bridge in years to come and provide a sense of pride forall those involved in the construction of Locking Castle Bridge. REFERENCES 1. Speci?cation for Highway W